Yarn tension controlling apparatus

ABSTRACT

A yarn tension controlling apparatus containing multi-staged yarn tensioning parts of surface friction and nip friction types arranged in sequence wherein large sized infeed yarn tension fluctuations are effectively compensated so as to result in smaller sized delivery yarn tension fluctuations with an effective prevention of possible hunting phenomenon in the compensating reaction.

United StatesPatent Yamamoto 1541 YARN TENSION CONTROLLING APPARATUS [72] Inventor: Atsunori Yamamoto, Onomichi,

4 Japan [73] Assignee: Nakao Kurosu, Hiroshima-ken,

Japan [22] Filed: June29, 1971 [21] Appl. No.: 157,846

[30] Foreign Application Priority Data Dec. 29, 1970 Japan ..45/120850 Dec. 29, 1970 Japan ......45/l2085l Dec. 29, 1970 Japan ..45/120852 52] us. Cl ..28/64 [51] Int. Cl. ..D8lh 19/22 [58] Field of Search ..28/64; 242/35.6

[56] References Cited UNITED STATES PATENTS 2,257,125 9/1941 Plourde ..28/6 X [451 Dec. 5, 1972 2,881,988 4/1959 Warwick ..28/64 X 3,119,571 1/1964 Pitts ..242/35.6 3,386,145

6/1968 Harris ..28/64 Primary Examiner-Louis K. Rimrodt Attorney-Milton .1. Wayne [57] ABSTRACT A yarn tension controlling apparatus containing multi-v staged yarn tensioning parts of surface friction and nip friction types arranged in sequence wherein large sized infeed yarn tension fluctuations are effectively compensated so as to result in smaller sized delivery yarn tension fluctuations with an effective prevention of possible hunting phenomenon in the compensating reaction. v

' 8 Claims, 20 Drawing Figures PATENTED DEC 5 m2 SHEET 7 0F 9 M i W TIME IN MIN Fig. /3

PATENTEU DEC 5 3.704.495

sum 9 or 9 YARN TENSION CONTROLLING APPARATUS The present invention relates to an improved yarn tension controlling apparatus, and more particularly it relates to a yarn tension controlling apparatus having multi-staged yarn tensioning parts of surface friction and nip friction types arranged in sequence.

In the field of textile industry, various kinds of yarn tensioning and/or yarn tension controlling apparatus have been developed so as to meet an important .requirement for constant yarn tension maintenance during yarn processing operations. One of the typical examples is found in the conventionaldisc-type tension controller, wherein the yarn is processed between a pair of superimposed tension discs. The two tension discs are put in a pressure contacting condition so as to restrain the tension fluctuation of the yarn passing therebetween. The pressure force is adjusted in view of the kind, type and thickness of the yarn to be processed prior to the commencement of the yarn processing. In conjunction with this mechanism, it should be noted that no positive control is applied to the setting of the yarn path passing through the tension controller. In the use of such apparatus, once an abnormal yarn tension fluctuation takes place exceeding the controllable limits, which are'forecast at the time of the initial pressure setting, any effectivetension control can never be expected. This is because the adjustment on the controller side does not follow the momentary fluctuation in the processing yarn tension. In other words, in a tension controller of this type, the controllable range of the yarn tension fluctuation is extremely narrow. Once the controller is adjusted for a certain processing condition, that adjustment of the controller is too difficult to be applied to another processingcondition of a different condition.

In view of the above-explained drawbacks the present invention provides a yarn tension controlling apparatus capable of ascertaining an effective yarn tension control following the momentary fluctuation of the yarn throughout the processing operation with an effective prevention of possible hunting phenomenon in the compensating reaction thereof.

The above-described object is attained by the apparatus of the present invention, wherein multi-staged yarn tensioning parts of surface friction and nip friction types are arranged in sequence and the yarn path therethrough is always controlled so as to minimize the infeed yarn tension fluctuation throughout the yarn processing operation. Possible hunting phenomenon in the tension compensating reaction is effectively and automatically prevented.

Further features and advantages of the invention will be made more apparent from the ensuing description, reference being made to the accompanying drawings, wherein;

FIG. 1 is a plan view of a typical embodiment of the present invention,

FIG. 2 is a side view taken along the FIG. 1,

line II-II in FIG. 3 is a partly-sectional view seen from the upstream side of the apparatus shown in FIG. 1,

FIG. 4 is a view of a yarn guide wire used in the present invention seen in the same direction as FIG. 3,

FIG. 5 is a sectional side view taken along the line VV in FIG. 1,

in FIG. 1 with part removed for clarity,

FIGS. 7A and 7B are views of the secondary tensioning part seen from the upstream and downstream sides, respectively,

FIGS. 7C and 7D are explanatory plan views for showing yarns paths through the secondary tensioning part,-

FIG. 8 is a side view seen from a side opposite to that in FIG. 2,

FIG. 9 is a view seen from the downstream side of the apparatus shown in FIG; 1,

FIG. 10 is an explanatory plan view of the yarn path downstream of the movable yarn guide of the present invention,

FIG. 11 is an explanatory view showing an angular turning of the movable yarn guide of the present invention,

FIG. 12 is a graphical drawing showing the damper effect bythe primary tensioning part of the present invention,

FIG. 13 is an explanatory view for showing the yarn breakage detecting mechanism of a modified embodi ment of the present invention, I iv v FIG. 14 is a view of another embodiment of the present invention seen from the downstream side,

- FIG. v1'5 is an explanatory .plan view of a further modified embodiment of the present invention shown in FIG. 1,

FIG. 16 is a sectional view of the apparatus shown in FIG. 15 seen in the same direction the same as FIG. 6 with part removed for clarity,

FIG. 17 is a plan explanatory view of the yarn processing on the apparatus shown in FIG. 15.

Referring to FIGS. 1 and 2, there is shown a typical embodiment of the yarn tensioning apparatus of the present invention. As concerns the externally visible structure, the apparatus includes, from upstream to downstream along the yarn processing direction, a primary tensioning part 1, a slub catcher part 2, a secondary tensioning part 3, a movable yarn guide 4 and a yarn delivery guide 6.

The primary tensioning part 1 includes a pair of cooperating nip rollers 7. and 8, which extend in a direction approximately perpendicular to the yarn processing direction, anda yarn guide wire 9 located to be spaced downstream ofthe nip rollers 7 and 8. As for the dispositions of the nip rollers 7 and 8, reference should be made to FIGS. 2 and 3. The nip rollers 7 and 8 are rotatably mounted on respective shafts 11 and 12. On the upstream side, the apparatus is provided with a lower front plate 13 secured to a pair of side plates 14a and 14b fixed to a body 16 (see FIG. 6) of the apparatus and an upper front plate 17 which is fixed to the side plates 14a and 14b via a supporter 18 (see FIG. 5) and a set screw 19. Both front plates 13 and ,17 are vertically spaced apart from each other permitting the disposition of the nip rollers 7 and 8 therebetween. Further, both front plates 13 and 17 are substantially located in a common vertical plane as seen from FIG. 5. As shown in FIG. 3, both plates 13 and 17 are respectively provided with vertically formed recesses 21 and 22 receptive of the upwardly and downwardly bent ends of the shafts 11 and 12 for supporting the nip rollers 7 and 8. It should be noted that the upper recesses 21 are deep enough to receive the upwardly bent ends of the shaft 11 while maintaining upper clearances 21a. In other words, the upper nip roller 7 therebetween. Owing to this floating mechanism, a-

possible yarn tension fluctuation of larger amplitude can be minimized by the nip of the two nip rollers 7 and 8. Accordingly, a primary tensioning of the yarn Y is carried out while the yarn Y is processed through this primary tensioning part 1. On a downstream face of the upper front plate 17, a yarn guide wire 9 of a shape such as shown in FIG. 4 is secured via a set screw 23. As is seen from FIG. 4, the yarn guide wire 9 has a yarn guide eye part 9a, a mounting part 9b and a curved part 9c for leading the yarn Y in the desired position forthe present invention.

After passing through the primary tensioning part 1, the yarn Y comes into theslub catcher part 2. As is seen from FIGS. 1 and 2, the slub catcher part 2-is mainly composed of 'a catcher roller 26 and a catcher rod 27, both extending'substantially vertically in parallel. The catcher roller 26 and the catcher rod 27 have a lower connection to an internal structure of the present invention, which will'be explained later in detail with reference to the illustration shown in FIG. 5.

The secondary tensioning part 3 is spaced to be located downstream from the slub catcher part 2. (see FIGS. 1 and 2) The secondary tensioning part 3 includes, as its major elements, a pressor disc 28 of a convex bottom face resting on a supporter surface member 29. The arrangement will be better understood from the illustration shown in FIG. 6. The pressor disc 28 is encircled, with slight clearances, by a wall 31 suitably secured to the side plates 14a and 14!). As is better seen from FIGS. 7A and 7B, the wall 31 is provided, on its upstream and downstream sides, with cut-offs 32a and 32b for guiding the processing yarn Y. The vertical edges of the cut-offs 32a and 32b approximately coincide with an upright imaginary center line of the pressor disc 28 passing through a contact point P of the pressor disc 28 with the surface member 29 as shown in FIGS. 7A and 73. Both cut-offs 32a and 32b open in a direction along which the yarn Y advances after passing around the movable yarn guide 4 (see FIG. 1). Therefore, within the region of the secondary tensioning part 3, the yarn Y always assumes a path extending only on one side of the contact point P as shown in FIG. 7C. That is, because the lateral movement of the yarn Y is hindered by the vertical edges of the cut-offs 32a and 32b, the yarn path does not move rightwards beyond the contact point P in FIG. 7C. Owing to this structural feature of the wall 32, the curved yarn portion is always urged towards the contact point P and is nipped between the approaching faces of the pressor disc 28 and the surface member 29. A compulsory yarn delivery overcoming this nip causes an exertion of frictional force on the yarn Y. The more the yarn path approaches the central contact point P, the larger the aforementioned frictional force operative on the yarn Y becomes and the larger the resultant yarn tension.

After passing through the secondary tensioning part 3, the yarn Y is furtherr advanced downstream via the movable yarn guide 4 and the yarn delivery guide 6.

Now, the internal structure of the present invention will be explained hereinafter in detail with reference back to the illustration in FIG. 5.

In the structure, a main shaft 33- extends from upstream to downstream through the body 16 of the apparatus. Located upstream outside the body 16 the main shaft 33 is provided with a threaded small diametr'al portion 33;: and a further reduced diametral extension 33b is'located furtherupstream and integral .of the portion'33a. The extension 33b is slidably received within a bearing 34 mounted in the lower front plate 13. Located downstream and outside the body 16, the main shaft 33 is provided with a partly threaded small diametral extension 330.

On the upstream side of the body 16, a supporter plate 36 and a pressor plate 37 are cooperatively mounted on the threaded small diametral portion 330 being pressed by a nut 38 to a stepped junction of the shaft 33 with the portion 33a. The-downward extensions of the catcher roller 26 and the catcher rod 27 are fixedly held bythe supporter plate 36 and the pressor plate 37. The catcher roller26 is rotatably inserted over its downward extension and the diametral size thereof can be selected freely according to the thickness of the processing yarn Y and the extent of the slubs to be caught in the slub catcher part 2. A rod .39 extends from upstream to downstream crossing over the secondary tensioning part 3 for rigidly connecting the catcher rod 27 with the movable yarn guide 4.

On the downstream side of the body 16, a supporter arm 41 for firmly upholding the movable yarn guide 4 is fixedly mounted on the small diametral extension 33c. In between the supporter arm 41 and the stepped junction of the extension 336 with the shaft 33, a spring hooker 42 and a cylinder 43 are inserted over the extension 33c and the three elements 41, 43 and 42 are pressed to the stepped junction by a set nut 44.

A larger cylinder 46 is disposed through an internal cavity of the body 16 and is provided, on the downstream outside of the body 16, with a flanged cylinder 47. A spiral spring 48 is inserted between the flanged cylinder 47 and the spring hooker 42 with its both ends fixed respectively to the two elements 42 and 47 Between the flanged cylinder 47 and the body 16, a later described supporter disc 49 of the yarn delivery guide 6 is rotatably inserted over the larger cylinder 46. A peripheral groove 53 is formed onan outer face of the larger cylinder 46 and a set screw 54 threaded through the body 16 is received in the groove 53. Therefore, the larger cylinder 46 is axially rotatable but not axially slidable.

Inside the larger cylinder 46, a bearing 51 is mounted for holding the main shaft 33 allowing the aforementioned axial sliding of the main shaft 33. On an upstream side of this hearing 51, there is inserted a smaller cylinder 52 over' the main shaft 33 in an arrangement slightly slidable along the main shaft 33..

The smaller cylinder 52 is provided with a spiral groove 56 formed on a peripheral face of it and a projection 57 fixed to the larger cylinder 46 is received inside the spiral groove 56. A flanged upstream end of the smaller cylinder 52 is provided with a pair of radially outward projections 58, which are slidably -received within elongated grooves 59 formed within the body 16. Owing to the wedge effect by these projections 58, axial rotation of the larger cylinder 46 does not induce axial rotation of the smaller cylinder 52. But, because of the engagement between the knock 57 and the spiral groove 56, an axial sliding of the smaller cylinder 52 is caused by the axial rotationof the larger cylinder 46.

In between the upstream flanged end of the smaller cylinder 52 and the downstream face of the supporter plate 36, there is provided a compression spring 6l encircling the main shaft 33; Now, the description will be directed to a damper-effect provided by the combination of the above-explained mechanical elements. Provided that the yarn tension is occasionally increased, both the movable yarn guide 4 and the catcher rod 27. tend to move leftwards in the arrangement shown in FIG. 7C. That is, the yarn Y tends to assume a path such as shown in FIG. 7D, wherein the yarn path is deviated from the central contact point P. This movement of the two elements 4 and 27 accordingly causes an axial rotation of the main shaft 33 and, via the spiral spring 48, this causes an axial rotation of the larger cylinder 46 (see FIG. 5). Owing to the connection of the larger and smaller cylinders 46 and 52 via the projection 57 and the peripheral groove 56, this rotation of the larger cylinder 46 causes upstream sliding of the smaller cylinder 52. This sliding naturally presses the compression spring 61 and accordingly, urges the supporter plate 36 upwardly. Because the supporter plate 36 is fixed to the main shaft 33, the main shaft 33 slides upwardly also. This sliding of the main shaft 33 accordingly accompanies upward movements of the associated elements 26, 27 and 4. By this sliding, the catcher roller 26 is brought into pressure contact with a downstream end of the supporter 18 of the upper front plate 17 and this pressure contact provides a kind of braking effect on the swinging movement of the movable yarn guide 4 and the catcher rod 27 about the main shaft 33. In other words, the above-mentioned internal structure provides a damper effect upon the excessive tion corresponding to the window 68. By turning the flanged cylinder 47 by hand, the larger cylinder 4.6 also turns and its peripheral numerical marks appear in the window 68 one by one. In the vicinity of the window 68, another indication window 67 is formed so as to show the extent of the axial sliding of the smaller cylinder 52. For this purpose, a seriesv of numerical marks are printed in a straight alignment at constant intervals on the periphery of the smaller cylinder 52 at an angular position corresponding to the indication win-. dow 67. As explained beforehand, an axial rotation of the larger cylinder 46 induces an axial sliding of the smaller cylinder 52 and following this sliding, the numerical marks on the periphery of the smallercylinder 52 appear in the window 67 one by one.

swinging movement of the yarn path defined by elements 4 and 27 responsive to the yarn tension fluctuation. That is, the possible hunting phenomenon can be minimized. The mode of this damper-effect is dependent on the spring characteristics of the spiral spring 48.

Further, the larger cylinder 46 is peripherally provided with ten radial holes 62 and a radial hole 63 is formed through the body 16 at a longitudinal position corresponding to the radial holes 62. The diameter of the hole 63 is slightly larger than that of the holes 62. Further, a ball 64, whose diameter almost conforms to that of the radial hole 63 is inwardly pressed towards the radial hole 62 by a compression spring 66 inserted in the hole 63. Provided that the ball 64 now meets a particular hole 62 and the flanged cylinder 47 is positively turned by hand, the larger cylinder 46 turns until the ball 64 comes into engagement with the next hole 62. However, once the ball 64 comes into engagement with a certain hole 62 and no such positive turning force is applied, the larger cylinder 46 retains its angular position throughout the yarn processing operation.

On a side of the apparatus opposite that shown in FIG. 2, an indication window 68 for showing the extent of the turning of the flanged cylinder 47 is formed through the body 16 and the side plate 14b of the apparatus as is seen from FIG. 8. On a periphery of the larger cylinder 46, a series of numericalmarks are printed with constant intervals at alongitudinal posi- As is shown in FIGS. 1, 2 and 9, the yarn delivery guide 6, which is provided in the form of an inverted 'U- shape wire, is fixed at its root portion to the supporter disc 49. This supporter disc 49 is rotatably inserted over the larger-cylinder 46 between the body 16 and the flanged cylinder 47 -(see FIG. 5). As is seen from FIG. 9, the supporter disc 49 is provided with a plurality of set holes 69 arranged, at constant intervals, near the peripheral fringe thereof. A set projection 71 (see FIG. 2), which is slidably placed within a recess of the body 16 being resiliently urged outwardly, is inserted into any one of the set holes 69. Through a suitable selection of the engagement between the set projection 71 and the set holes 69, the yarn delivery guide 6 can be fixed at selected angular positions with respect to the main shaft 33. In other words, a yarn path extending between the movable yarn guide 4 and the yarn delivery guide 6 can be selected as desired.

As to the adequate angular setting of the yarn delivery guide 6, reference should be made to FIG. 10. In the illustration, the movable yarn guide 4 is shown to exert a force T, on the yarn Y and the tension of the yarn Y under delivery ,is shown to be T An included angle formed between the yarn path from the element 4 to the element 6 and the moving direction to the element 6 is shown to be 6. Then the following mathematical relationship is established'between the two forces T and T So, if magnitudes of the forces T, and T are known before the setting of the supporter disc 49, the value of the included angle 0 can be easily calculated from the above-presented mathematical equation.

Now, the operation of the apparatus of the present invention will be explained in detail with reference to the above-explained structural features thereof.

In the first place, the supporter disc 49 is turned over and is fixed at a desired angular position by inserting set projection 71 into the corresponding set hole 69. Next,

. 7 guide 4 is so selected that the numerical markis l or larger.

At the time of initiating the yarn path through the apparatus, the movable yarn guide 4 is firstly brought by hand to the position designated by and the yarn'Y is placed between the position 0,,and 0,. Upon release of the yarn guide 4, the yarn guide 4 automatically resumes the position 0 due to the resilient force applied by the spiral spring 48. Following this movement of the yarn guide 4, the yarn Y is placed in a condition such as shown in FIG. I and the leading end of the yarn Y is further conducted downstream via the yarn delivery guide 6. When the yarn Y is processed along this course, the yarn is subjected to a tension force on a supply side, a nip frictional force by the nip rollers 7 and 8, a frictional forceby the pressor disc 28 resting'on the supporter surface member 29 and a frictional force by the movable yarn guide '4. The tension on the yarnY on-the .delivery side is given in the form of avector sum of the aforementioned forces. Due to this determined. yarn delivering tension, the urging force by the spiral spring 48 is overcome and the yarn Y tends to assume a path'remotely spaced from the contact point P as shown in FIG. 7D. This results in the corresponding reduction in the frictional force operable on the yarn in the secondary tensioning part 3 (see FIG. 2). Furthenthis causes a corresponding reduction in the yarn delivering tension. In response to this reduction in the yarn delivering tension, the movable yarn guide'4 tends to return to its initial angular position due to the resilient urging force by the spiral spring 48 and the yarn path in the secondary tensioning part 3 approaches the contact point P. This approach leads to the increase in the frictional force by the pressor disc 28 and accordingly, the increase in the yarn delivering tension. After several times of repetition of the abovementioned steps, the resultantyarn delivering tension balances the movable yarn guide 4 urging force by the spiral spring 48. Similar procedure will take place when the yarn supply tension fluctuates and the balance is establishedbetween the yarn delivering tension and the urging force by the spiral spring 48. Therefore, should the urging force by the spiral spring 48 be retained as constant, the yarn delivering tension can be assuredly controlled as constant regardless of the possible fluctuation in the yarn supplying tension.

Now, explanation will be made of the damper effect on the present invention, reference being made to FIG. 12. In the drawing, the time-functional change of the yarn tension upstream of the primary tensioning part 1 (see FIG. 2) is shown by a curve A whereas that of the yarn downstream of the primary tensioning part 1 is shown by a curve B. As is already mentioned, the floating mechanism of the upper nip roller 7 (see FIG. 3) provides a damper effect on the fluctuation of the yarn tension. This damper effect is clearly seen in FIG. 12, wherein the amplitude S of the curve B is considerably reduced from the amplitude S of the curve A. However, as is seen in the illustration, there still remains an appreciable extent of the tension fluctuation, which fluctuation is further minimized through the already explained axial sliding of the main shaft 33 (see FIG. This axial sliding of the main shaft 33 results in the pressure contact between the catcher roller26 and the supporter 18 and because the movable yarn guide 4 is rigidly connected to the catcher roller 26 via the rod 39, this pressure contact gives a braking'effect on the excessive turning movement of the movable yarn guide 4. The magnitude of the contact pressure is proportionalto the magnitude of the .force exerted on the spiral spring 48. t

As a modification of the basic inventional concept; the apparatus can be accompanied with a function of detecting possible yarn breakages. Such a modified embodiment will be better understood by referring to FIGS. 5 and 13. Firstly in FIG. 5, a'set screw 73 is threaded into the lower front plate 13 so as to fix the bearing 34. In the present embodiment, the main shaft 33, the bearing 34, the supporter plate 36, the pressor plate 37 and the side plates 14a and 14b must be made up of electro-conductive materials, whereas the flanged cylinder 47, the larger cylinder 46, the smaller cylinder 52 and the lower front plate 13 must be made up of non-conductive materials. v

Now, in FIG. 13, when the yarn Y assumes its normal path, the catcher rod :27 assumes a position 0,, and there exists no electric connection between the side plates 14a, 14b and the elements 36, 37 shown in FIG 5. Accordingly, the set screw 73 is electrically insulated from the side plates 14a and 14b.'

Upon breakage of the yarn Y, the catcher rod 27 comes to a position 0 due to the urging force by the spiral spring 48 and lower corner X of the elements 36, 37 comes in contact with the side plate 14b and this contact establishes an electric circuit between the set screw 73 and'the side plate 1412.

It is possible, that the yarn tension escalates abnormally just preceding the yarn breakage on, for example, a warper. Under this situation, the catcher rod 27 assumes a position 0 and other lower corners X come in contact with the other side plate 14a so as to establish the same electric circuit. The electric circuits thus established can be connected to a suitable alarm device of known structure.

In the above-mentioned embodiments of the apparatus, the angular position of the yarn delivery guide 6 is fixed as desired prior to the commencement of the yarn processing through a selected combination of the set projection 71 with one of the set holes 69. Such selected angular position of the yarn delivery guide 6 is retained throughout the yarn processing operation until the next selected combination. In other words, the angular position of the guide 6 is not changeable throughout the yarn processing operation unless a new selection thereof is effected again. This constant angular position of the guide 6 often introduces trouble to a winding of the yarn in a cheese form. Especially when a yam of a relatively resilient nature is wound in a cheese form under a constant yarn tension, a non-uniform density of the yarn mass in the cheese configuration often results and it lowers the commercial value of the product. In an extremely bad situation, the winding operation itself becomes difficult to be continued. In order to obviate such trouble, it is necessary to lower the yarn tension continuously corresponding to the growth of the cheese.

An embodiment for such effect is illustrated in FIG. 14, wherein the supporter disc 49 of the guide 6 is provided with partial peripheral gear teeth 76. The gear teeth 76 are associated with a driver gear 77 meshing f t A A therewith. The driver gear 77 is connected to a-pulse motor (not shown). Upon recep-tion of pulse signals corresponding to the growth of the cheese under winding, the pulse motor rotates the driver gear 77 in such a fashion that the supporter disc 49 will be rotated in a direction to reduce the yarn tension. Aside from the pulse motor, any known driving mechanism for this effect.can be suitably adopted. When one cycle of cheese building is completed, the supported disc 49 is reversely rotated by the driver gear 77 so as to resume its initial angular position.

When the yarn tension is'abnormally increased, the mechanism shown in FIG. 13 functions and suitable signals informative of the tension increase may be issued for an automatic and/or manual elimination of the causes of the tension increase. However, under certain situations in the actual yarn processing, it is often desired to instantly stop the yarn advancement upon occurrence of the yarn tension increase. For example, on a warper, it is highly desirable not towind the yarn of abnormal tension on the beam. Such instant stoppage of the yarn delivery can beeffected through positively cutting the yarn upon yarn tension increase. It is further known, as briefly mentioned in the foregoing description, that the yarn tension abnormally escalates just prior to the possible yarn breakage. Therefore, the possible yarn breakage can be forecast if the abnormal yarn tension increase is sensed beforehand.

An embodiment of the apparatus of such function is shown in FIGS. 15 and 16, wherein a nipper plate 78 is fixed on the supporter surface member 29 with its upwardly bent end facing the normal yarn path. It should be noted that the nipper plate 78 is located on a same side of the contact point P of the pressor disc 28 with the delivery side of the yarn Y downstream of the yarn delivery guide 4. Downstreamly spaced from the nipper plate 78, a cutter blade 79 is fixed. to the surface member 29 on the same side of the contact point P with the nipper blade 78 with its cutter fringe directing the normal yarn path.

As to the function of the illustrated embodiment, reference should be made to FIG. 16. In the .illustra tion, when the yarn tension assumes normal magnitudes, the yarn Y runs along a path Y whereas, when the yarn tension abnormally escalates the elements 4, 26 and 27 are urged upwardly in the drawing overcoming the resilient force by the spiral spring 48 (see FIG. and the yarn Y assumes a path Y (see FIG. 17) being caught by the nip. plate 78. Concurrently with this, the yarn Y contacts the cutter blade 79 so as to be severed thereby. As to the limit value of the abnormal yarn tension at which the yarn path changes as abovementioned, suitable selection to the initial angular position of the supporter disc 49 decides such a limit value. U

Further, when a slub portion of the yarn Y arrives at the slub catcher part 2, an increased frictional force on the yarn Y by the elements 26 and 27 induces corresponding abnormal increase of the yarn tension, which is followed by the above-explained yarn cutting operation. Due to the inherent inertia of 'the mechanism and the urging force by the resilient ele ment, an appreciable length of time is needed for the yarn to change its path from Y, to Y In other words, the slub portion must have an appreciable length. So, when the yarn is provided with nep portions, which are of relatively small length, but not with slub portions,

the yarn will pass through the apparatus without being cut by the cutter blade 79. This is a very different point of the structure of the present invention from theconventional slub catchers, wherein an exact catch of the slub portions inevitably induces unnecessary cutting of the yarn at nep portions.

What is claimed is:

1. An improved yarn tension controlling apparatus comprising, in combination, a primary tensioning part including a pair of nip rollers, one of which floatingly rests on the other, extending almost perpendicularly to a yarn path; a slub catcher part located spacedly downstream of said primary tensioning part and involving a pair of parallel upright members spacedly sandwiching said yarn path, a secondary tensioning part located downstream of said slub catcher part and in-' volving a pressor disc of a convex bottom face resting on a contact surface, which is formed on a bodyof said apparatus, with said yarn path extending between said bottom face and said flat surface; a movable yarn guide located downstream of said secondary tensioning part; an axially turnable main shaft elongated from upstream to downstream through said body-on which shaft both of said slub catcher part and movable yarn guide are fixedly mounted; means for urging said movable yarn guide resisting a yarn tension and disposed to said main shaft; and a yarn delivery guide located downstream of said movable yarn guide so as to define a yarn delivering path from said apparatus.

2. An improved yarn tensioning apparatusas claimed in claim 1, wherein said pressor disc bearing contact surface is of a flat structure.

3. An improved yarn tensioning apparatus as claimed in claim 1, wherein said movable yarn guide urging means is of a resilient structure.

4. An improved yarn tensioning apparatus as claimed in claim 1, wherein said movable yarn guide urging means is of a counter-weight structure. I

5. An improved yarn tensioning apparatus as claimed in claim 1, wherein said main shaft is mounted within said body in an axially slidable arrangement, an excessive turning of said main shaft caused by a possible yarn tension fluctuation induces an axial sliding of said main shaft, this axial sliding causes a pressure contact of said slub catcher part with said primary tensioning part and this pressure contact exerts a braking effect on said excessive turning of said main shaft.

6. An improved yarn tensioning apparatus as claimed in claim 1, further comprising a supporter disc for fixedly upholding said yarn delivery guide and mounted axially turnable about said main shaft; and a mechanism for fixing an angular position of said supporter disc about said main shaft. H U V 7. An improved yarn tensioning apparatus as claimed in claim 1, further comprising a supporter disc for fixedly upholding said yarn delivery guide and mounted axially turnable about said main shaft; and a mechanism for positively turning said supporter disc in proportion to a growth of a take-up cheese.

8. An improved yarn tensioning apparatus as claimed in claim 1, further comprising a nipper plate fixed to 

1. An improved yarn tension controlling apparatus comprising, in combination, a primary tensioning part including a pair of nip rollers, one of which floatingly rests on the other, extending almost perpendicularly to a yarn path; a slub catcher part located spacedly downstream of said primary tensioning part and involving a pair of parallel upright members spacedly sandwiching said yarn path; a secondary tensioning part located downstream of said slub catcher part and involving a pressor disc of a convex bottom face resting on a contact surface, which is formed on a body of said apparatus, with said yarn path extending between said bottom face and said flat surface; a movable yarn guide located downstream of said secondary tensioning part; an axially turnable main shaft elongated from upstream to downstream through said body on which shaft both of said slub catcher part and movable yarn guide are fixedly mounted; means for urging said movable yarn guide resisting a yarn tension and disposed to said main shaft; and a yarn delivery guide located downstream of said movable yarn guide so as to define a yarn delivering path from said apparatus.
 2. An improved yarn tensioning apparatus as claimed in claim 1, wherein said pressor disc bearing contact surface is of a flat structure.
 3. An improved yarn tensioning apparatus as claimed in claim 1, wherein said movable yarn guide urging means is of a resilient structure.
 4. An improved yarn tensioning apparatus as claimed in claim 1, wherein said movable yarn guide urging means is of a counter-weight structure.
 5. An improved yarn tensioning apparatus as claimed in claim 1, wherein said main shaft is mounted within said body in an axially slidable arrangement, an excessive turning of said main shaft caused by a possible yarn tension fluctuation induces an axial sliding of said main shaft, this axial sliding causes a pressure contact of said slub catcher part with said primary tensioning part and this pressure contact exerts a braking effect on said excessive turning of said main shaft.
 6. An improved yarn tensioning apparatus as claimed in claim 1, further comprising a supporter disc for fixedly upholding said yarn delivery guide and mounted axially turnable about said main shaft; and a mechanism for fixing an angular position of said supporter disc about said main shaft.
 7. An improved yarn tensioning apparatus as claimed in claim 1, further comprising a supporter disc for fixedly upholding said yarn delivery guide and mounted axially turnable about said main shaft; and a mechanism for positively turning said supporter disc in proportion to a growth of a take-up cheese.
 8. An improved yarn tensioning apparatus as claimed in claim 1, further comprising a nipper plate fixed to said contact surface with its yarn nipping end facing said yarn path and a cutter blade fixed to said contact surface with its yarn cutting fringe facing said yarn path. 